The safest most foolproof way is to wait on the OTA. Unlocking, rooting and flashing, although very simple, will always carry some risk. The good news is the GNex is virtually unHARDbrickable. There is a bunch of tutorials which will make it easy and painless. Good luck and peace out.

This is by far the best resource I've found. I used this to root, and unlock, and flash my phone. I was very hesitant at first, but now I'm applying updates every few days. Titanium Backup is the best for backing up all your settings, but you need to be rooted. Otherwise make sure everything is backed up to a google account and you wont lose much.